Drive device, lens barrel, image pickup apparatus, lens drive method and method of producing shape memory alloy

ABSTRACT

A lens barrel, an image pickup apparatus, a lens drive method and a method of producing a shape memory alloy used for the drive device are disclosed. A drive device includes: a lens group for guiding light from a subject; a shape memory alloy adopted to be deformed by an electricity supplied to the shape memory alloy, for moving the lens group in a direction of an optical axis; and electricity-supply controlling means for controlling an amount of the electricity supplied to the shape memory alloy; and a detecting means for detecting whether a movement of the lens group starts or not. In the drive device, a movement amount of the lens group in the direction of the optical axis is controlled based on the amount of electricity supplied when the detecting means detects the movement of the lens group.

RELATED APPLICATIONS

This is a continuation of application Ser. No. 11/990,253, filed Feb. 7,2008 which is a U.S. National Phase Application under 35 USC 371 ofInternational Application PCT/JP2006/315261 filed on Aug. 2, 2006.

This application claims the priority of Japanese application nos.2005-232920 filed Aug. 11, 2005, 2005-239758 filed Aug. 22, 2005 and2005-265023 filed Sep. 13, 2005, the entire content of all of which ishereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a drive device constructed to move alens group representing a driven body by using expansion and contractionof a shape memory alloy, a lens barrel, an image pickup apparatus, alens drive method and a method of producing a shape memory alloy usedfor the drive device.

BACKGROUND ART

With regard to the shape memory alloy (hereinafter referred to sometimesas “SMA”), even if it is plastically deformed due to receiving force ina temperature not higher than martensitic transformation completiontemperature, it recovers its shape when it is heated to the temperaturethat is not less than reverse transformation completion temperature.

FIG. 23 is a diagram wherein a relation between temperature anddeformation of the shape memory alloy is graphed schematically. In FIG.23, the horizontal axis represents temperature (° C.) and the verticalaxis represents deformation (%).

As shown in FIG. 23, when electricity is supplied between both ends ofthe shape memory alloy at a low temperature, the shape memory alloy iscontracted by generated heat to return to its memorized length. On theother hand, when the electricity supply stops at the state of this hightemperature, the temperature of the shape memory alloy decreases due toheat radiation, and its length changes with hysteresis to become thestate of elongated again. The shape memory alloy is possible to use asan actuator by utilizing this effect of shape memory, and there havebeen made various proposals.

However, actions of a shape memory alloy (SMA) are provided by heatingSMA with Joule heat through supplying electricity for SMA, and therebyobtaining displacement of a driven member by utilizing a deformationcorresponding to the temperature resulted from the heating. Therefore,it has been difficult to determine the unique input condition for SMA toobtain desired displacement, because of various un-uniformity in theconstituted system such as, for example, errors in a length of SMA,errors in a resistance value of SMA, errors of mechanical dimensions ofconstituent members and the ambient temperature.

For dissolving the aforesaid problems, therefore, there has beenproposed a position-control drive device that detects a position of alens group representing a driven body, and partially changes the shapememory alloy based on the results of the detection (for example, seeJapanese Patent Publication Open to Public Inspection No. 10-307628).

Further, Japanese Patent Publication Open to Public Inspection (JP-A)No. 11-324896 discloses a drive mechanism that detects the ambienttemperature with a temperature sensor, and controls a current value anda voltage value to be supplied to a wire formed by a shape memory alloy,or controls a duty ratio of a pulse current or of a pulse voltage to besupplied to the wire, based on the detected result.

Further, JP-A No. 2002-99019 discloses a drive mechanism using astring-like shape memory alloy which is formed to be in a dogleggedshape to be in contact with a driven body at the substantial centerposition of the string-like shape memory alloy and to be fixed at bothends of the string-like shape memory alloy.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The position control drive device in the aforesaid JP-A No. 10-307628 issuitable to drive a lens group with being arranged in a lens barrel of adevice such as a camera. However, when it is applied to a lens drivedevice of a small-sized and thin image pickup apparatus provided to behoused in, for example, a mobile terminal, there are needed positiondetecting sensors for acquiring information about the present positionof a driven member to be arranged on the total area where the drivenmember moves, resulting in slight disadvantage for downsizing and costreduction, which is a problem.

In the drive mechanism described in the aforesaid JP-A No. 11-324896, itis suitable to be utilized at the inside of the apparatus wheretemperature distribution is relatively uniform such as a rear cover of acamera. However, when it is applied to a lens drive device of asmall-sized and thin image pickup apparatus provided to be housed in,for example, a mobile terminal, circuit parts that operate otherfunctions are arranged densely in the vicinity of the drive mechanism,whereby, temperature distribution in the apparatus is not uniform, anddetection values vary depending on a position where a temperature sensoris arranged. Thus, it is sometimes provide a situation hardly to conductoptimum control.

Further, the drive mechanism described in JP-A No. 2002-99019 wherein astring-like shape memory alloy which is formed to be in a dogleggedshape is used, is not so problematic for mounting in a large equipmentsuch as binocular glasses. However, it requires any other ideas forapplying the drive mechanism to a small-sized image pickup apparatus tomount it in a mobile terminal, because fixed sections on both ends areprotruded greatly from both sides of a driven body.

It is known that the shape memory alloy occurs an initial creepphenomenon that a deformation amount changes depending on the number oftimes of supplying electricity at the initial step where the frequencyof supplying electricity is small. When a drive device utilizing a shapememory alloy controls a position of a driven body, the deformationamount changes unwillingly even when applying the same amount ofcurrent, because of the aforesaid initial creep phenomenon. Therefore,there is also in a problem that accurate position control is difficult.

In view of the aforesaid problems, an object of the invention is toobtain a small-sized and low-cost drive device that employs a shapememory alloy for an actuator, and can stop a lens group at a desiredposition and is suitable to be mounted in a mobile terminal; a lensbarrel; an image pickup apparatus; a lens drive method; and a method ofproducing a shape memory alloy used for the drive device.

Means to Solve the Problems

The aforesaid problems are solved by the structures listed below:

1. A drive device comprising: a lens group for guiding light from asubject; a shape memory alloy adopted to be deformed by an electricitysupplied to the shape memory alloy, for moving the lens group in adirection of an optical axis; an electricity-supply controlling meansfor controlling an amount of the electricity supplied to the shapememory alloy; and a detecting means for detecting whether a movement ofthe lens group starts or not,

wherein a movement amount of the lens group in the direction of theoptical axis is controlled based on the amount of the electricitysupplied when the detecting means detects the movement of the lensgroup.

2. A drive device comprising: a lens group for guiding light from asubject; a shape memory alloy adopted to be deformed by an electricitysupplied to the shape memory alloy, for moving the lens group in adirection of an optical axis; an electricity-supply controlling meansfor controlling an amount of the electricity supplied to the shapememory alloy; and a detecting means for detecting a movement of the lensgroup at the two predetermined positions,

wherein a movement amount of the lens group in the direction of theoptical axis is controlled based on each of amounts of the electricitysupplied when the detecting means detects the movement of the lens groupbetween two predetermined positions along the optical axis.

3. The drive apparatus of Item 1 or 2, wherein the detecting means is anoutput of an image pickup element.4. A drive device comprising: a driven body; a shape memory alloyengaged with the driven body; a heating section for heating the shapememory alloy; a controlling section for controlling a drive of thedriven body by controlling the heating section,

wherein the controlling section applies an aging treatment to the shapememory alloy when the shape memory alloy is initially used, the agingtreatment controlling the heating section to repeat a predeterminednumber or more of times of heating and no-heating processes.

5. The drive device of Item 4, wherein the heating section heats theshape memory alloy by applying an electric current to the shape memoryalloy.6. A drive device comprising: a driven body; a shape memory alloyengaged with the driven body; a heating section for heating the shapememory alloy; a controlling section for controlling a drive of thedriven body by controlling the heating section,

wherein the shape memory alloy is applied an aging treatment in advance,the aging treatment repeating a predetermined number or more of times ofheating and no-heating processes.

7. The drive device of Item 6, wherein the shape memory alloy is heatedby applying an electric current to the shape memory alloy.8. A lens barrel comprising: a lens group for guiding light from asubject; a lens frame supporting the lens group; and a shape memoryalloy formed in a shape of a string for moving the lens frame in apredetermined direction,

wherein a part of the shape memory alloy is arranged in an optical pathof the lens group, and

the shape memory alloy moves the lens frame by being contracted due toan electricity supplied to the shape memory alloy.

9. The lens barrel of Item 8, wherein the shape memory alloy moves thelens frame in a direction of an optical axis by being contracted.10. The lens barrel of Item 9, wherein the shape memory alloy moves thelens frame close, to the subject by being contracted.11. The lens barrel of Item 10, wherein the lens frame is pressed towardan image-forming surface.12. An image pickup apparatus comprising the drive apparatus of any oneof Items 1 to 7.13. An image pickup apparatus comprising the lens barrel of any one ofItems 8 to 11.14. A lens drive method of driving a lens group for controlling anamount of a movement of a lens group for guiding light from a subject inan optical axis, by controlling the lens group, a shape memory alloy,and an amount of an electricity supplied to the shape memory alloy, themethod comprising:

a step of gradually changing an electricity supplied to the shape memoryalloy and detecting whether a movement of the lens group starts or not;

a step of determining an amount of an electricity to be supplied to theshape memory alloy which is needed to move the lens group to apredetermined position based on an amount of an electricity suppliedwhen the movement of the lens group starts; and

a step of supplying the electricity which is determined to the shapememory alloy.

15. A lens drive method of driving a lens group for controlling anamount of a movement of a lens group for guiding light from a subject inan optical axis, by controlling the lens group, a shape memory alloy,and an amount of an electricity supplied to the shape memory alloy, themethod comprising:

a step of gradually changing an electricity supplied to the shape memoryalloy and detecting a movement of the lens group at two predeterminedpositions along the optical axis;

a step of determining an amount of an electricity to be supplied to theshape memory alloy which is needed to move the lens group to apredetermined position based on each of amounts of the electricitysupplied when the movement of the lens group are detected at the twopredetermined positions; and

a step of supplying the electricity which is determined to the shapememory alloy.

16. A method of producing shape memory alloy for use in a driveapparatus comprising a driven body, a shape memory alloy connected tothe driven body, a heating section for heating the shape memory alloy, acontrolling section for controlling a drive of a driven body bycontrolling the heating section, the method comprising: a step ofapplying an aging treatment to the shape memory alloy, the agingtreatment repeating a predetermined number or more of times of heatingand no-heating processes.17. The method of producing shape memory alloy of Item 16, wherein theshape memory alloy is heated by applying an electric current to theshape memory alloy.

Effects of the Invention

The invention makes it possible to obtain a small-sized and low costdrive device that has a simple and convenient structure and can stop alens group at a desired position accurately, a lens barrel, an imagepickup apparatus, a lens drive method and a method of producing a shapememory alloy used for the drive device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an appearance diagram of a cell-phone representing an exampleof a mobile terminal equipped with an image pickup apparatus relating tothe present embodiment.

FIG. 2 is a perspective view of an image pickup apparatus provided as aunit relating to the present embodiment.

FIG. 3 is a sectional view showing an internal structure of the imagepickup apparatus.

FIG. 4 is a perspective view showing the inside of the image pickupapparatus.

FIG. 5 is a front view showing arrangement of respective parts insidethe image pickup apparatus.

FIG. 6 is a schematic diagram showing relationship for respective partsabout which the string-like shape memory alloy is extended.

Each of FIGS. 7( a), 7(b), and 7(c) is a diagram showing an initialstate (no-electricity state) of each part of the lens drive devicerelating to the first embodiment.

FIG. 8 is a flow chart showing a lens drive method of an image pickupapparatus relating to the first embodiment.

FIG. 9 is a graph showing relationship between an amount of current fora shape memory alloy and deformation of the shape memory alloy, whichshows a method of determining the amount of current.

FIG. 10 is a flow chart showing a lens drive method of an image pickupapparatus relating to the second embodiment.

FIG. 11 is a graph showing relationship between an amount of current fora shape memory alloy and deformation of the shape memory alloy, whichshows a method of obtaining relationship between an amount of lensmovement and an amount of current.

FIG. 12 is a diagram showing another example of a detecting device thatdetects a movement of a lens group at two predetermined locations in theoptical axis direction.

FIG. 13 is a conceptual diagram showing relationship between deformationamount E and temperature T when electricity is supplied at the firsttime and the tenth time.

FIG. 14 is a conceptual diagram showing relationship between an amountof deformation and the number of times of supplying electricity.

FIG. 15 is a diagram showing a control block of a drive device in thepresent embodiment.

FIG. 16 is a diagram showing a control routine of a drive device in thepresent embodiment.

FIG. 17 is a diagram showing an aging control routine.

FIG. 18 is a front view showing another example of arrangement ofrespective parts constituting a lens barrel inside an image pickupapparatus.

Each of FIGS. 19( a) and 19(b) is a sectional view of the lens barrelinside the image pickup apparatus shown in FIG. 18 which is taken on aplane including the shape memory alloy.

Each of FIGS. 20( a) and 20(b) is an illustration diagram wherein anoptical path is interrupted by the shape memory alloy.

FIG. 21 is a top surface diagram of a leaf spring of a diaphragm type.

Each of FIGS. 22( a) and 22(b)a sectional view in which a shape memoryalloy is extended.

FIG. 23 is a diagram wherein relationship between temperature anddeformation of a shape memory alloy is graphed schematically.

EXPLANATION OF NOTATION

-   11. Lens group-   12. Cover member-   13. Bottom plate-   15, 16. Guide shaft-   17. First lens frame-   18. Second lens frame-   19. Helical compression spring-   21. Screw-   23. Shape memory alloy-   31. Print board-   32. Flexible print board-   34. Image pickup element-   41. Photo-interrupter-   100. Image pickup apparatus

BEST MODE FOR CARRYING OUT THE INVENTION

The invention will be explained in detail as follows, referring to theembodiment, to which, however, the invention is not limited.

FIG. 1 is an appearance diagram of a mobile phone T which is an exampleof a mobile terminal provided with the image pickup apparatus relatingto the present embodiment.

In the mobile phone T shown in FIG. 1, an upper casing 71 as a caseprovided with the display image screens D1 and D2, and the lower casing72 provided with operation buttons P, are connected with each otherthrough a hinge 73. The image pickup apparatus 100 is housed below thedisplay image screen D2 in the upper casing 71, and the image pickupapparatus 100 is arranged in such a manner that the light can betaken-in from the outer surface side of the upper casing 71.

Hereupon, this image pickup apparatus 100 may also be arranged above oron the side surface of the display image screen D2 in the upper casing71. Further, it is of cause that the mobile phone is not limited to afolding type.

FIG. 2 is a perspective view of an image pickup apparatus relating tothe present embodiment in the state provided as a unit.

As shown in FIG. 2, an outer surface of the image pickup apparatusrelating to the embodiment is composed of box-shaped cover member 12that has an opening so that lens group 11 may take in light from asubject; bottom plate 13 that fixes thereon the cover member 12 throughscrew 14 and holds respective members arranged inside; print board 31that is fixed on the bottom surface of the bottom plate 13, and holdstherein image pickup elements mounted therein; and flexible print board32 that is connected to the print board 31. There is further arrangedflexible print board 32 f for supplying electric power to a shape memoryalloy which will be explained later. Further, the flexible print board32 f is connected also to photo-interrupter 41 that is fixed on thebottom plate 13. This flexible print board 32 f may either beconstructed integrally with the flexible print board 32 or beconstructed separately from the flexible print board 32.

Incidentally, on the flexible print board 32, there is formed contactpoint section 32 t for connecting to another board of a mobile terminal,and reinforcing plate 33 is pasted on the reverse side of the flexibleprint board 32. Now, the symbol O represents an optical axis of lensgroup 11. Further, the contact point section 32 t represents an elementwhich has 20 pins or more such as a power supply, control signals, imagesignal output and a terminal for inputting to a shape memory alloy, andit is shown schematically.

Next, internal structures of the image pickup apparatus relating to thepresent embodiment will be explained as follows, referring to FIGS. 3, 4and 5. Incidentally, in the following figures, the same symbols aregiven to the same function members for the explanation.

FIG. 3 is a sectional view showing the internal structures of the imagepickup apparatus. FIG. 3 shows a section taken on line F-F in FIG. 2.

FIG. 4 is a perspective view showing the inside of the image pickupapparatus. FIG. 4 shows a situation wherein cover member 12, print board31 and flexible print board 32 and 32 f are removed from image pickupapparatus 100 shown in FIG. 2.

FIG. 5 is a front view showing arrangement of respective partsconstituting a lens barrel inside the image pickup apparatus. FIG. 5 isa diagram wherein the image pickup apparatus shown in FIG. 4 is viewedfrom the subject side in the optical axis direction.

Inside the image pickup apparatus 100, there are arranged the first lensframe 17 (hereinafter referred to as lens frame 17) that houses thereinlens group 11 that is composed of a single lens or of plural lenses, andthe second lens frame 8 (hereinafter referred to as lens frame 18) thatholds the lens frame 17 in the outside of lens frame 17.

The lens frame 17 is engaged with the lens frame 18 through screwsections 17 n and 18 n, and the lens frame 17 can be moved in theoptical axis direction against the lens frame 18 when the lens frame 17is rotated on the lens frame 18. Incidentally, the lens frame 17 and thelens frame 18 may also be arranged so that both of them may be movedrelatively in the optical axis direction through a helicoid or throughother structures.

The bottom plate 13 is formed to be a quadrangle substantially when itis viewed in the optical axis direction. Guide shafts 15 and 16 arelocated at almost diagonal positions with in-between optical axis O onthe bottom plate. Guide shaft 15 is planted in the bottom plate 13 to bein substantially parallel with the optical axis, and guide shaft 16 isintegrally formed with the bottom plate as one body. Alternatively, theguide shaft 15 may also be integrally formed as one body with the bottomplate 13 and the guide shaft 16 may be planted in the bottom plate 13.

Cylindrical section 18 p through which the guide shaft 15 is engaged andis penetrated is integrally formed as one body on the lens frame 18, andU-shaped engaging section 18 u that engages with the guide shaft 16 isformed on the lens frame 18. Owing to this, the lens frame 18 can movein the optical axis direction along the guide shafts 15 and 16, and lensframe 17 and lens group 11 can move together with the lens frame 18 inthe optical axis direction. Further, this cylindrical section 18 p ispressed by helical compression spring 19 representing a pressing memberin the axial direction of the guide shaft 15. In the present example,the cylindrical section 18 p is pressed toward image pickup element 34arranged in the rear of the lens group 11.

Further, there is integrally formed light-shielding plate 18 s on thecylindrical section 18 p of the lens frame 18 as one body. Thislight-shielding plate 18 s is arranged in the optical path of lightemitted from or received by photo-interrupter 41 that is fixed on thebottom plate 13 with screw 42. Thus, the light-shielding plate 18 s ismoved by a movement of the lens frame 18 in the optical axis direction,to shield the optical path of light emitted from or received byphoto-interrupter 41, or to retreat from the optical path of lightemitted from or received by photo-interrupter 41.

Further, there is integrally formed protrusion section 18 t on the sideof the lens frame 18 as one body. On the other hand, boss 20 is formedon the bottom plate 13, and flat-head screw 21 is screwed in anunillustrated hole of the boss 20. The protrusion section 18 t is incontact with a head portion of this screw 21. Namely, the lens frame 18is pressed toward the image pickup element side by compression coilspring 19 representing a pressing member, and a position of the lensframe 18 on the image pickup element side is determined when theprotrusion section 18 t touches the head portion of the screw 21 that isa contact member arranged on the bottom plate 13.

Two columnar sections 22 are integrally formed on the bottom plate 13 asone body. These two columnar sections 22 are formed at the position tobe arranged at both ends of a line connecting optical axis O of lensgroup 11 to a center line of the cylindrical section 18 p. Both ends ofshape memory alloy 23 which is in a string shape are fixed on the twocolumnar sections 22. The string-like shape memory alloy 23 is extendedwith being in contact with a bottom portion of the lens frame 18 closerto image pickup element 34 between optical axis O of lens group 11 andthe cylindrical section 18 p.

FIG. 6 is a schematic diagram showing relationship for respective partsabout which the shape memory alloy formed in a string shape is extended.

As shown in FIG. 6, both ends of shape memory alloy 23 formed in astring shape are fixed on the two columnar sections 22 which areintegrally formed on the bottom plate 13 as one body. The shape memoryalloy 23 formed in a string shape is extended in a way so that it comesin contact with a bottom portion of the lens frame 18 at about thecenter portion thereof, after angles of the shape memory alloy 23 formedin a string shape are changed by a part of the columnar section 22 to besymmetrical from both of the fixed portions.

Further, each of the both end portions of the shape memory alloy 23formed in a string shape is cut with being held by plate member 23 k,and this plate member 23 k is fixed at the upper portion of the columnarsection 22.

When predetermined current or voltage is applied to the shape memoryalloy 23 thus extended, from flexible print board 32 f (see FIG. 2)through the plate member 23 k, the shape memory alloy 23 representing aresistive element generates heat to raise its temperature, and itchanges to shorten its total length, namely, it is contracted. Due tothis, the lens frame 18 can be moved in the optical axis direction Oalong guide shafts 15 and 16, resisting helical compression spring 19representing a pressing member. Namely, lens group 11 held by lensframes 18 and 17 can move toward a subject along optical axis O toadjust a focal position with a shorter distance.

The foregoing is the internal structure of the image pickup apparatus100 relating to the present embodiment.

Next, a drive device and a drive method for moving lens group 11 ofimage pickup apparatus 100 having the aforesaid structure housed incell-phone T will be explained as follows.

First Embodiment

First, a lens drive device and a lens drive method relating to the FirstEmbodiment will be explained. In the First Embodiment, the presence orabsence of movement of a lens group is detected by gradually changingelectricity supplied to a shape memory alloy. Based on an amount ofelectricity supplied at a point in time when the movement is detected,an amount of the electricity to move the lens group by a predeterminedamount in the optical axis direction is determined, and then, drivecontrol for the lens group is conducted.

Each of FIGS. 7( a), 7(b) and 7(c) is a diagram showing an initial state(state of no-electricity) of each part of lens drive device 100 relatingto the First Embodiment. FIG. 7( a) is a diagram schematically showingpositional relationship between light-shielding plate 18 s andphoto-interrupter in the initial state, FIG. 7( b) is a diagram showingoutput of photo-interrupter 41 and FIG. 7( c) is a diagram showingrelationship between lens frame 18 and shape memory alloy 23.

First, lens frame 18 of image pickup apparatus 100 is adjusted so thatit may be located at its predetermined position, and a position of thelight-shielding plate 18 s is adjusted so that a part of a light fluxemitted from or received by photo-interrupter 41 may be shielded asshown in FIG. 7( a). This adjustment is conducted by rotating flat-headscrew 21 and by moving the touching protrusion section 18 t in theoptical axis direction (see FIGS. 4 and 5).

More closely, a position of the lens frame 18 is determined by flat-headscrew 21 so that a position of the light-shielding plate 18 s may agreewith a position in a range of illustrated D representing a transitionarea between the state of shielding and the state of retreating causedby light-shielding plate 18 s within an area where light is emitted fromor received by photo-interrupter 41 shown in FIG. 7( b), namely, aposition of the light-shielding plate 18 s may agree with a positionwhere the light-shielding plate 18 s shields a part of a light fluxemitted from or received by photo-interrupter 41.

Next, focal point is adjusted by moving lens frame 17 in the opticalaxis direction O by rotating the lens frame 17 on lens frame 18. A focalpoint of lens group 11 held by lens frame 17 is adjusted so that, forexample, a subject positioned at a hyperfocal distance may be focused onan image pickup surface of image pickup element 34. In this case, theshape memory alloy 23 is in the tensional state against lens frame 18 asshown in FIG. 7( c). A component in the optical axis direction of forceapplied on SMA is small, thus, the shape memory alloy 23 remainsstationary under the condition that the shape memory alloy 23 iselongated slightly by pressing force of helical compression spring 19,and that protrusion section 18 t of the lens frame is in contact with ahead of screw 21. Incidentally, SMA may also be in the state havingslight slackness between itself and lens frame 18.

Namely, the lens drive device 100 relating to the First Embodiment isadjusted so that a subject positioned at a hyperfocal distance may befocused under the state of no-electricity. Incidentally, this focusposition is not limited to only to the hyperfocal distance, and it mayalso be a position where a subject positioned at an infinite distance isfocused. However, in the present embodiment, an explanation is givenunder the condition of an adjustment where a subject positioned at ahyperfocal distance is focused.

FIG. 8 is a flow chart showing a lens drive method of image pickupapparatus 100 relating to the First Embodiment. The present embodimentis described with following the flow chart shown in FIG. 8.

In FIG. 8, it is confirmed whether a photographing mode is set or not(step S101). When the mode other than the photographing mode isdesignated due to certain operations (step S101; No), the photographingmode is terminated (step S120) and the flow moves to the other modewhich is designated (step S121).

When the photographing mode is set (step S101; Yes), the image pickupelement is driven to display preview images (which are also calledthrough images) on a display screen on a real time basis (step S102).Then, the flow is in a state waiting for an operation that a buttoncorresponding to a release button among buttons on a cell-phone isturned on (step S103). When a button corresponding to a release buttonis not turned on (step S103; No), the flow returns to step S101.

When a button corresponding to a release button is turned on (step S103;Yes), an image for evaluating focus is taken in (step S104). It meansthat the image for evaluating focus taken in at step S104 is an image onthe occasion where a lens group is at a hyperfocal position.

Then, a current value set in advance is applied to the shape memoryalloy (step S105), and an output of a photo-interrupter is judgedwhether it changes or not (step S106). When the output of thephoto-interrupter does not change (step S106; No), a current whose valueincreases from the current value applied previously by a predeterminedincrement amount is applied to the shape memory alloy (step S107). Then,an output of a photo-interrupter is judged again whether it changes ornot (step S108). When the output of the photo-interrupter does notchange (step S108; No), the flow returns to step S107, a current whosevalue further increases from the current value applied previously by apredetermined increment amount is applied to the shape memory alloy, andjudgment whether the output of the photo-interrupter changes at stepS108 or not is repeated.

It means that a current value applied to the shape memory alloygradually increases until the moment when the output of thephoto-interrupter changes. The current value at which the output of thephoto-interrupter starts changing means that the current value at whicha component in the optical axis direction of force that acts on theshape memory alloy exceeds pressing force in the optical axis directionby helical compression spring 19, and protrusion section 18 t of thelens frame leaves a head of screw 21.

When the output of the photo-interrupter changes (step S108; Yes), acurrent amount to be applied to the shape memory alloy for moving a lensgroup to a predetermined position (macro position) is determined basedon the current value on that occasion (step S109). The amount of currentthus determined is applied to the shape memory alloy (step S110). Themethod of determining an amount of current in step S109, for example, isdescribed below.

FIG. 9 is a graph showing relationship between a current amount for ashape memory alloy and deformation of the shape memory alloy, andshowing a method of determining a current amount. The horizontal axisrepresents the current value, and the vertical axis represents thedeformation.

When a current value I_(a1) is obtained at a point of time when anoutput of the photo-interrupter is changed, current value I_(a2) whichis increased by a prescribed amount from the current value I_(a1) isapplied to the shape memory alloy. On the other hand, when a currentvalue I_(b1) is obtained at a point of time when an output of thephoto-interrupter is changed, current value I_(b2) which is increased bya prescribed amount from the current value I_(b1) is applied to theshape memory alloy. By doing this, it is possible to move lens frame 18from its initial state by a predetermined amount. Namely, it is possibleto move a lens group from a position for focusing to hyperfocal distanceto a position for macro photographing.

By employing the structure, as stated above, determining an amount ofelectricity to move the lens group to the position for macrophotographing based on the current value at the point of time when anoutput of the photo-interrupter changes, and supplying the amount ofelectricity to the shape memory alloy, it is possible to dissolvemicroscopic errors in a length of the shape memory alloy, mountingerrors and un-uniformity of an amount of movement of lens group causedby ambient temperatures, and to obtain an image pickup apparatus whichdoes not provides individual difference when moving a lens group to amacro position.

Incidentally, though a method of determining a current value in stepS109 has been explained by using a graph, it is naturally possible toemploy those using a lookup table and to employ those determining bycalculation.

Returning to the flow in FIG. 8, the lens group moves to the macroposition in step S110. At this position, an image for evaluating focusis taken in (step S111). Then, two images taken in at step S104 and stepS111 are evaluated (step S112).

Then, a lens group is set at the position where the image having largerhigh-frequency component between two images in evaluation in step S112(step S113). Specifically, when the image for evaluation obtained instep S104 has larger high-frequency component, applying current to theshape memory alloy is stopped and a lens group is positioned in theinitial state, namely, the lens group is located at the position forfocusing to the hyperfocal distance. When the image for evaluationobtained in step S111 has larger high-frequency component, the currentvalue determined in step S110 is applied to the shape memory alloy, andthe lens group is located at the macro photographing position.

Then, photographing and image recording on a recording material areconducted at the lens group position established in step S113 (stepS114), and the flow returns to step S101.

As explained above, by detecting whether the movement of the lens grouphas started or not while gradually changing an amount of electricitysupplied to the shape memory alloy, then, by determining an amount ofelectricity to move the lens group to a desired position, based on theamount of electricity at the time when the movement starts, and byapplying the amount of electricity thus determined to the shape memoryalloy, it is possible to dissolve microscopic errors in a length of theshape memory alloy, mounting errors and un-uniformity of an amount ofmovement of lens group caused by ambient temperatures, and to obtain alens drive device which does not provide individual difference whenmoving a lens group to a macro position, and thereby to obtain asmall-sized and low-cost image pickup apparatus wherein the structure issimple, and a lens group can be stopped accurately at a desiredposition.

Incidentally, although the explanation has been given about the positioncontrol for two points including a hyperfocal position and a macroposition, in the aforesaid explanation, it is also possible to provide astructure such that plural current values each being increased fromI_(a1) are established stepwise, to be capable of being stopped atplural steps of lens positions. Further, though the explanation uses theexample wherein a position for detecting changes of output of aphoto-interrupter and a hyperfocal position of the lens are at thesubstantially same position, the present invention is not limited tothis. A position of the lens which is protruded by a prescribed distancefrom the hyperfocal position may also be set as a position for detectingchanges of output of a photo-interrupter.

Further, though the explanation has so far been given referring to theexample of a self-focusing image pickup apparatus, the invention canalso be applied to manual setting as the followings: when the hyperfocalposition is selected, the electricity does not supplied to the shapememory alloy, while, when a macro position is selected, a position of alens group is set manually by following operations of step S105—stepS110 in FIG. 8.

Further, in the aforesaid example, a photo-interrupter is used to detectwhether the movement of the lens group has started or not. However, itis also possible to provide a structure, for example, to monitor apredetermined area of preview images continuously, and a point of timewhen the focusing condition changes is regarded as the time of startingmovement.

Second Embodiment

In the Second Embodiment, movement of the lens group is detected at twolocations by gradually changing current values to be supplied to theshape memory alloy. Based on the amounts of electricity at points oftime when movement of lens group were detected at two predeterminedpositions, an amount of electricity necessary for moving the lens groupto the desired position is determined, and then, drive control for thelens group is conducted.

Initial state (state of no-electricity) of each section of lens drivedevice 100 is the same as one shown in FIGS. 7( a), 7(b), and 7(c), andit is preferable that light-shielding plate 18 s approaches the verylimit of an optical path for emitting light from or receiving light on aphoto-interrupter, and shields neither emitted light nor received light.

FIG. 10 is a flow chart showing a lens drive method of image pickupapparatus 100 relating to the Second Embodiment. An explanation will begiven as follows, referring to the flow chart shown in FIG. 10.

In FIG. 10, it is confirmed whether a photographing mode is set or not(step S201). When the mode other than the photographing mode isdesignated due to certain operations (step S201; No), the photographingmode is terminated (step S220) and the flow moves to the other modewhich is designated (step S221).

When the photographing mode is set (step S101; Yes), a current value setin advance is applied to the shape memory alloy (step S202), and outputof a photo-interrupter is judged whether it is changed or not (stepS203). When output of a photo-interrupter changes (step S203; Yes), theapplied current value is stored (step S204).

When the output of the photo-interrupter does not change (step S203;No), a current whose value increases from the current value appliedpreviously by a predetermined increment amount is applied to the shapememory alloy (step S205). Then the output of the photo-interrupter isjudged again whether it changes or not (step S206).

When the output of the photo-interrupter does not change (step S206;No), the flow returns to step S205, and a current whose value furtherincreases from the current value applied previously by a predeterminedincrement amount is applied to the shape memory alloy, and judgment tocheck whether the output of the photo-interrupter changes or not (stepS206) is repeated.

When the output of the photo-interrupter changes (step S206; Yes), theapplied current value is stored (step S207). Then, it is judged whetherthe number of the stored current values becomes two (step S208). When itremains to be one (step S208; No), the flow returns to step S205 and acurrent whose value further increases from the current value appliedpreviously by a predetermined increment amount is applied to the shapememory alloy, to repeat step S205 and step S206 until the output of thephoto-interrupter changes again. When the number of the stored currentvalue becomes two (step S208; Yes), the flow moves to step S209, andrelationship between an amount of lens movement and an amount of currentis obtained from two current values obtained. The relationship obtainedin the step S209 is as follows.

FIG. 11 is a graph showing relationship between an amount of current anddeformation that shows a method of obtaining relationship between anamount of lens movement and an amount of current. The horizontal axisrepresents a current value and the vertical axis represents deformation.

Output of the photo-interrupter changes, at the first time, at the pointof time when light-shielding plate 18 s united with lens frame 18 startsmoving to the subject side in the optical axis direction from theinitial state shown in FIG. 7( a). Output of the photo-interrupterchanges, at the second time, at the point of time when thelight-shielding plate 18 s retreats from an area for light emitted fromor light received on a photo-interrupter after moving toward the subjectside in the optical axis direction. Namely, with respect to the storedtwo current values, the first current value is one at the point of timewhen a component in the optical axis direction of force applied to shapememory alloy exceeds pressing force in the optical axis direction byhelical compression spring 19 and protrusion section 18 t of lens frameleaves a head portion of screw 21; and the second current value is oneat the point of time when lens frame 18 is moved by an amount equivalentto a thickness in the optical axis direction of light-shielding plate 18s.

In FIG. 11, a current value I_(c1) is obtained at the point of time whenthe output of a photo-interrupter changes first time, and a current valeI_(c2) is obtained at the point of time when the second output of aphoto-interrupter changes. When the current value increases from I_(c1)to I_(c2), a deformation factor is changed, which means that lens frame18 is moved by an amount equivalent to a thickness in the optical axisdirection of light-shielding plate 18 s by changes of illustrated H.

Namely, when a thickness of light-shielding plate 18 s is represented byA (mm), a current value to move lens frame 18 by B (mm) in the opticalaxis direction from the initial state shown in FIGS. 7( a), 7(b), and7(c) is expressed by I_(c1)+B(I_(c2)−I_(c1))/A.

Owing to the foregoing, it is possible to obtain a current value to movelens frame 18, namely, lens group 11 from a position of the initialstate to the position on the subject side in the optional optical axisdirection.

Returning to the flow in FIG. 10, electricity to the shape memory alloyis stopped (step S210) after storing relationship obtained in step S209.Owing to this, lens frame 18 is restored to the initial state.

Then, when it is judged again whether a photographing mode is set or not(step S211) and the photographing mode is not set (step S211; No), theflow returns to step S201. While, when the photographing mode is set(step S211; Yes), an image pickup element is driven, and a preview image(which is also called a through image) is displayed on a display screenon a real time (step S212). Then, a button corresponding to a releasebutton among buttons on a cell-phone is on standby to be turned on (stepS213). When the button corresponding to a release button is not turnedon (step S213; No), the flow returns to step S211.

When the button corresponding to a release button is turned on (stepS213; Yes), an image for evaluating focusing is taken in first (stepS214). Namely, the image for evaluating focusing which is taken in atstep S214 is an image when a lens group is at a hyperfocal position.

Then, relationship between a current amount to be applied to a shapememory alloy obtained in the foregoing and an amount of movement of alens frame is used to obtain a current value to move the lens group tothe desired lens position, and this current value is applied to theshape memory alloy (step S215). Due to this, the lens group is movedfrom its initial position to a desired focusing position on the shortdistance side. At this position, an image for evaluating focusing istaken in (step S216).

Incidentally, when plural focusing positions on the short distance sidehas been set, a current value to move to each lens position is obtainedand step S215 and step S216 are repeated, thereby, an image forevaluating a focus is taken in at each position.

Then, images for evaluation taken in at step S214 and at step S216 areevaluated (step S217).

The lens group is set at the position at which evaluation at step S217was obtained, for example, at which an image having larger highfrequency component among obtained images for evaluation was obtained(step S218). Specifically, when an obtained image for evaluation at stepS214 contains larger high frequency component, applying of a current tothe shape memory alloy is stopped. The lens group is set to the initialstate, namely, a lens group is set at a position where the lens group isfocused at a hyperfocal position. When any of images for evaluationobtained in step S216 contains larger high frequency component, the lensgroup is set to state wherein an amount of current to move the lensgroup to the position where the aforesaid image was obtained is appliedto a shape memory alloy.

Then, photographing and recording of images on a recording medium areconducted at the position where the lens group was set in step S218(step S219), and the flow returns to step S201.

In other words, the Second Embodiment is one wherein a current value tomove a lens group by an amount determined in advance is detected, andbased on this, an amount of current to move to the desired position isobtained.

As explained above, by providing a structure wherein a movement of alens group is detected at two predetermined positions in the opticalaxis direction while gradually changing electricity supplied to theshape memory alloy, and an amount of electricity to move a lens group tothe desired position is determined based on the amount of electricity ateach of these two positions, and a lens group is moved to the desiredposition by supplying the determined amount of electricity to the shapememory alloy, it is possible to dissolve fluctuations of an amount ofmovement of the lens group caused by errors in length of the shapememory alloy, errors in mounting and by ambient temperatures, and toobtain a lens drive device which does not provides individual differencewhen moving a lens group, to obtain a small-sized and low cost imagepickup apparatus that can stop the lens group accurately at the desiredposition with a simple structure.

Further, by detecting the movement at two positions, it is possible toconduct accurate position control, even when fluctuations of inclinationin characteristic curves caused by un-uniformity of pressing force ofhelical compression spring and by un-uniformity of wire diameter of theshape memory alloy are generated, which is different from the occasionwhere detection is conducted at one position.

Incidentally, although the explanation has been given referring to theexample of the self-focusing image pickup apparatus, the invention canbe applied also the occasion of manual setting. In this case, changingthe steps S214-S218, when the hyperfocal position is selected,electricity to the shape memory alloy is stopped, while, when the focusposition on the desired short distance side is selected, a current valueto move the lens group to the designated lens position is obtained fromthe relation acquired in step S209, and it is applied to the shapememory alloy. Thus, it is possible to conduct manual setting.

Further, although the explanation has been given referring to theoccasion where the initial setting of the lens group is on thehyperfocal position, it is also possible to use a position for focusingon infinity in place of the hyperfocal position, or, it is furtherpossible to position the lens group on the image pickup element side.

In the foregoing, current values at two positions wherephoto-interrupter outputs changes were obtained before taking in imagesfor evaluation, in the structure. However, the invention is not limitedto this, and current values may also be obtained after the step S213, orit is also possible to obtain current value with a change of the firstphoto-interrupter output before step S213 and to obtain current valuewith a change of the second photo-interrupter output after step S213.

FIG. 12 is a diagram showing another example of a detecting device thatdetects a movement of a lens group at prescribed two positions in theoptical axis direction.

As shown in FIG. 12, sheet member 43 having flexibility is fixed on lensframe 18. It is preferable that the sheet member 43 is made of amaterial having light shielding effect.

An edge portion on one side of the sheet member 43 is superposed asillustrated on an area of pixels that are not used for image amonglight-receiving pixels of the image pickup element 34, to shield a lightflux of a subject coming from lens group 11. If lens frame 18 is movedfrom this state in the optical axis direction, the sheet member 43 fixedon the lens frame 18 is moved in the direction of the illustrated arrow,and pixel output of the pixel area that is not used as an image ischanged.

Namely, by monitoring pixel output of image pickup element 34 whilegradually changing electricity supplied to shape memory alloy 23, and bydetecting the change of pixel output on the pixel area that is not usedfor image, a start of movement of the lens group can be detected.Further, when movement between prescribed number of pixels is detectedby the sheet member 43, movement of a lens group can be detected atprescribed two positions in the optical axis direction.

By providing this structure, it is possible to detect movement of a lensgroup without adding a new member such as a photo-interrupter, andthereby to make an image pickup apparatus to be lower cost.

Though the explanations were given in the aforesaid First and SecondEmbodiments referring to those wherein a current value changes whenelectricity supplied to the shape memory alloy, the invention is notlimited to this. It is naturally possible to employ the structurewherein voltage is changed or a current value is fixed with duty ratiobeing changed. Further, the shape memory alloy, as described above,provides an initial creep phenomenon wherein a deformation amountchanges with the number of times of turning electricity on in theinitial stage where the frequency of turning electricity on is small.The initial creep phenomenon is described as follows.

FIG. 13 is a conceptual diagram showing relationship between deformationamount s and temperature T when the electricity is supplied at the firsttime and the tenth time. FIG. 13 shows an occasion wherein a prescribedload weight is impressed on a string-like shape memory alloy to change atemperature of the shape memory alloy in order of T2, T1, and T2 (whereT1<T2). A deformation amount represented by the vertical axis indicatesa rate of an elongated length at each frequency to the string length attemperature T2 at the start, which is defined as the standard.

As shown in FIG. 13, a deformation amount when electricity is suppliedat the tenth time is smaller than that at the first time. For example, adeformation amount ε1 is obtained when electricity is supplied at thetenth time in the occasion of lowering a temperature from T2 to T1. Thedeformation amount ε1 is smaller than ε2 that is a deformation amountwhen the electricity is supplied at the first time.

FIG. 14 is a conceptual diagram showing relationship between adeformation amount and the number of times of supplying electricity.FIG. 14 shows an occasion wherein a prescribed load weight is applied toa string-like shape memory alloy, and prescribed current is applied tothe shape memory alloy for the prescribed length of time to turn thecurrent ON and to the prescribed length of time to turn the current OFF.A deformation amount represented by the vertical axis indicates a rateof an elongated length to the string length when the electricity isturned on at first time, which is defined as the standard.

As shown in FIG. 14, a deformation amount during the electricity isturned ON is greatly changed up to the moment of about (ten-odd)^(th)electricity supply. These phenomena mean that accurate position controlis difficult, because an amount of distortion is changed undesirablyeven when the same current is applied, until the moment of about(ten-odd)^(th) electricity supply.

It is preferable to do as follows for coping with the initial creepphenomenon described above. FIG. 15 is a diagram showing a control blockof a drive device in the present embodiment. Control section 50 controlsa current to be applied to shape memory alloy 23 through current supplycircuit 52, based on an amount of lens barrel movement inputted fromlens barrel movement amount input section 51. In the control section 50,there is provided memory section 501 that is constituted with anonvolatile memory such as EEPROM that stores the number of times ofsupplying electricity one after another.

FIG. 16 is a diagram showing a control routine of a drive device in thepresent embodiment. Control section 50 judges first whether an agingaction completion flag is set on memory section 501 in control section50 or not (S1). When the aging action completion flag is judged to beset (S1; Yes), the control section 50 jumps to ordinary control routine(S3), and controls a current to be applied to shape memory alloy 23through current supply circuit 52, based on an amount of lens barrelmovement inputted from lens barrel movement amount input section 51. Onthe other hand, when the aging action completion flag is judged not tobe set (S1; No), the control section 50 jumps to aging control routine(S2).

FIG. 17 is a diagram showing an aging control routine.

First, control section 50 sets electricity-supply frequency i=0 as aninitial setting (S21). Next, the control section 50 applies a prescribedamount of current (for example, 80 mA) to shape memory alloy 23 throughcurrent supply circuit 52 for a prescribed period of time (for example,0.5 sec.) (S22). Next, the control section 50 stops applying current tothe shape memory alloy 23 through current supply circuit 52 for aprescribed period of time (for example, 1.0 sec.) (S23). Next, thecontrol section 50 increments electricity-supply frequency i by one(S24). Next, the control section 50 judges the electricity-supplyfrequency i whether it has arrived at a prescribed frequency or not(S25). When the electricity-supply frequency i is judged to have arrivedat the prescribed frequency (S25; Yes), the control section 50 sets theaging action completion flag on memory section 501 (S26) to terminatethe routine. When the electricity-supply frequency i is judged not tohave arrived at the prescribed frequency (S25; No), the flow returns toS22, and steps S22-S25 are repeated until the electricity-supplyfrequency i arrives at the prescribed frequency.

Incidentally, the prescribed frequency may be set to the frequency atwhich a deformation amount is stabilized, and there is no upper limitfor the prescribed frequency.

As stated above, by operating the aging treatment by repeatingprescribed number of switching of electricity-supply between ON and OFF,an amount of deformation for applied current is stabilized as seen inFIG. 14. It enables, in the control thereafter, to provide accurateposition control by setting an amount of current to be applied to theshape memory alloy based on an amount of lens barrel movement.

Incidentally, though heating and no-heating processes for the shapememory alloy were repeated by joule heat that is generated due tocurrent applied to the shape memory alloy, it is also possible toexternally repeat heating and no-heating processes.

Though the aging processing was applied to shape memory alloy 23 aftercompletion of assembly of an image pickup apparatus unit, the agingprocessing for the shape memory alloy can be conducted by externalheating process, for example, at any time before sheet member 23 k isfixed on both edge portions, or before mounting on columnar section 22,or before pressing by helical compression spring 19. In particular,aging processing can be conducted either under the state where the shapememory alloy is stressed, or under the state where the shape memoryalloy is not stressed.

In the aforesaid embodiment, the explanation was given referring to theexample wherein the string-like shape memory alloy 23 is in contact witha bottom portion of lens frame 18 on the image pickup element 34 sidebetween optical axis O of lens group 11 and cylindrical section 18 p, tobe extended, as shown in FIG. 5. However, the invention is not limitedto this, and the following structure can also be employed.

FIG. 18 is a front view showing another example of arrangement ofrespective parts constituting a lens barrel inside an image pickupapparatus. FIG. 18 will be partially explained about only a portionwhich is different from the image pickup apparatus shown in FIG. 5.

In the image pickup apparatus shown in FIG. 18, two columnar sections 22are formed to be standing on bottom plate 13, and they face each otherwith optical axis P in-between. Both end portions of shape memory alloy23 formed to be in a string shape are interposed and fixed on columnarsections 22 by plate member 23 k. Then, both end portions of the shapememory alloy 23 are connected to the flexible print board through theplate member 23 k.

A central portion of the shape memory alloy 23 is arranged to be capableof touching a rear end portion of the second lens frame 18 on the imagepickup element 34 side (image forming surface side). Therefore, theshape memory alloy 23 is extended under the condition that the centralportion is arranged in the optical path of lens group 11.

Each of FIGS. 19( a) and 19(b) is a sectional view of the lens barrelinside the image pickup apparatus shown in FIG. 18 which is taken on aplane including the shape memory alloy. FIG. 19( a) is a diagram showinga situation wherein no electricity is supplied to shape memory alloy 23,and FIG. 19( b) is a diagram showing a situation wherein electricity issupplied to shape memory alloy 23, and lens group 11 is protruded.

As shown in FIG. 19( a), a protrusion section on the rear end of thesecond lens frame 18 is in contact with a receiving surface of bottomplate 13. As a result, when no-electricity is supplied to shape memoryalloy 23, lens group 11 is stationary located at a certain position, andan image of a subject is formed on image pickup element 34. Therefore,if the focal position of the lens group 11 is adjusted at a hyperfocaldistance, it is possible to take a photograph that is in focus for thedistance covering from infinity to a half of a hyperfocal distance.

Under the aforesaid condition, if an electricity is applied to the shapememory alloy 23 through plate member 23 k, the shape memory alloy 23representing a resistor generates heat and its temperature rises, andits total length contracts to be shortened. Owing to this, the secondlens frame 18 is guided by guide shafts 15 and 16 against pressing forceof helical compression spring 19, to be moved to the subject side thatis opposite to image pickup element 34, as shown in FIG. 19( b). Namely,lens group 11 that is held by the first lens frame 17 through the secondlens frame 18 is moved to the subject side along optical axis O.Therefore, it is possible to focus an image of a subject that is in ashorter distance onto image pickup element 34.

It is therefore recommended that no-electricity is supplied to shapememory alloy 23 in the case of long-range photographing andintermediate-range photographing, and that electricity is applied toshape memory alloy 23 in the case of close-range photographing such asphotographing flowers.

Further, in the case where an image pickup apparatus has an AF functionand where manual setting of distance for long-range and close-range isstructured to be possible, electric power to be supplied to the shapememory alloy can be adjusted in many steps depending on a photographingdistance.

Since the shape memory alloy 23 is arranged in the condition to crossoptical axis O of lens group 11, and the second lens frame 18 is presseduniformly, the second lens frame 18 can be moved in the optical axisdirection efficiently. Incidentally, though an example wherein the shapememory alloy 23 is arranged in the condition to cross optical axis O oflens group 11 in the illustration, the shape memory alloy 23 can also beextended to avoid the optical axis.

Incidentally, the central portion of the shape memory alloy 23 mentionedabove means a portion that is not an edge portion, and it does not meanthe center position that is at equal distance from both ends.

Further, in the aforesaid structure, a central portion of the shapememory alloy 23 is arranged in the optical path of lens group 11.Therefore, a part of the optical path is interrupted by the shape memoryalloy 23, and it becomes difficult to see an image, depending onconditions. A way of solving this problem will be explained based onFIGS. 20( a) and 20(b).

Each of FIGS. 20( a) and 20(b) is an illustration diagram wherein anoptical path is interrupted by the shape memory alloy. FIG. 20( a) is adiagram wherein the shape memory alloy 23 is arranged in the opticalpath of lens group 11, and FIG. 20( b) is a diagram wherein the shapememory alloy 23 is viewed in the optical axis direction.

First, it is known that, if a size of a subject arranged in the opticalaxis of an image pickup lens is 3% or less of an area of the opticalaxis crossing the subject, an image of the subject is difficult to beobserved even when the image is formed on an image pickup element.

When D represents a diameter of the optical path at a position where theshape memory alloy 23 is arranged in the optical path of lens group 11,and d represents a diameter of the shape memory alloy 23, as shown inFIG. 20( b), an area of the optical path is πD²/4, and an area of theshape memory alloy 23 in the optical path is d·D. Therefore, thefollowing conditional expression (1) is to be satisfied.

d·D/(πD ²/4)<0.03  (1)

This conditional expression (1) can be simplified as follows.

d/D<0.02  (2)

Incidentally, for satisfying the conditional expression (2), it ispreferable to arrange the shape memory alloy 23 at the position where anarea of the optical path in the vicinity of a final surface of lensgroup 11 is large. However, if an arrangement is constituted so that animage of the shape memory alloy 23 formed on image pickup element 34 maybe removed by an image processing, the conditional expression (2) doesnot always need to be satisfied.

According to circumstances, the shape memory alloy may either bearranged between lenses of an image pickup lens having plural lenses, orbe arranged on the subject side of the image pickup lens.

Further, there is a possibility that a cell-phone housing therein animage pickup apparatus employing the shape memory alloy of this kind isused under the condition of high temperature. Therefore, it ispreferable to make up the constitution wherein the shape memory alloy 23is arranged to be loosened slightly so that the second lens frame 18 maynot be advanced even if the shape memory alloy 23 shrinks at thetemperature of 50-60° C. or the temperature lower than that, and theshape memory alloy 23 shrinks when the temperature becomes 100° C., forexample, to touch rear end portion 18 d and the second lens frame 18 maybe advanced.

A lens barrel having the structure that is different from the foregoingwill be explained as follows, referring to FIGS. 21, 22(a) and 22(b).FIG. 21 is a top surface diagram of a flat-head spring of a diaphragmtype, and each of FIGS. 22( a) and 22(b) is a sectional view in which ashape memory alloy is extended. FIG. 22( a) is a diagram showing thesituation where an electricity is not supplied to the shape memory alloy23, while, FIG. 22( b) is a diagram showing the situation whereelectricity is applied to the shape memory alloy 23 and lens group 11 isprotruded. The present lens barrel is similar to the aforesaid lensbarrel on the point that the shape memory alloy 23 is extended with itscentral portion being arranged in the optical path of lens group 11, andboth ends thereof are respectively fixed on columnar section 22. On theother hand, a different point is one wherein the second lens frame 18has no engagement section 18 d, guide shafts 15 and 16 are not providedto stand on bottom plate 13, and helical compression spring 19 is notprovided.

First, leaf spring 25 of a diaphragm type shown in FIG. 21 is made ofphosphor bronze or of stainless steel. Leaf spring 25 have steps in thedirection of a center axis on flat portion 25 a on the outercircumferential side and on flat portion 25 c on the innercircumferential side, and flat portion 25 a and to flat portion 25 c isconnected to each other with inclined portion 25 b. Therefore, leafspring 25 has a spring function due to deformation of the inclinedportion 25 b.

As shown in FIGS. 22( a) and 22(b), leaf spring 25 is fixed on the upperreverse side of cover member 12 and on the upper end portion of thesecond lens frame 18, and further, the same leaf spring 26 is fixed onprotrusion section on the rear end of the second lens frame 18 and onbottom surface 13 e of bottom plate 13. Spring pressure of leaf spring25 is greater than that of leaf spring 26. Therefore, whenno-electricity is supplied to the shape memory alloy 23, leaf spring 25presses the second lens frame 18 against leaf spring 26 to cause areverse side of leaf spring 26 to touch receiving surface 13 b of bottomplate 13, thus, lens group 11 is positioned in the optical axisdirection, as shown in FIG. 22( a). Further, when the shape memory alloy23 is supplied for close-range photographing, the shape memory alloy 23contracted, thereby, the second lens frame 18, namely, lens group 11 isprotruded to the prescribed position against leaf spring 25.

Though the occasion of using leaf spring 25 of a diaphragm type is alsothe same as the occasion of using the aforesaid helical compressionspring 19 in terms of basic function, the second lens frame 18, thefirst lens frame 17 and lens group 11 can be supported without tiltingan optical axis, by using two leaf springs 25 and 26, and thereby, guideshafts 15 and 16 are made redundant, which makes a lens barrel to besmaller than that in the aforesaid structure.

Incidentally, in the aforesaid structure, the shape memory alloy 23 doesnot always need to cross optical axis O, but it is preferable to cross alocation that is as close as possible to optical axis O.

The orientation for the shape memory alloy to move a lens group in theoptical axis direction is not always limited to that toward the subjectside, and it is also possible to constitute to move toward the imageforming surface side according to circumstances. For example, a lensgroup is arranged so that it may be in the depth of field only forclose-range, and the lens group is moved toward the image formingsurface side when photographing for the long-range including infinity.

It is also possible to provide a structure so that a lens may be movedin the direction perpendicular to its optical axis for a lens movementfor correction of shake of an image pickup apparatus and for a movementof a lens converter. Even in the case of the structure of this kind, ashape memory alloy is arranged in an optical path of a lens group.However, what is arranged in an optical path of a lens group is notalways a central portion of the shape memory alloy, but a part of theshape memory alloy is arranged in the optical path of the lens group.

Incidentally, in the aforesaid explanation, there was used an examplewherein the first lens frame 17 and the second lens frame 18 areprovided. However, it is also possible to employ an example wherein thefirst lens frame 17 and the second lens frame 18 are integrated.

1-17. (canceled)
 18. A method of producing shape memory alloy for use ina drive apparatus comprising a driven body, a shape memory alloy incontact with the driven body, a heating section for heating the shapememory alloy, a controlling section for controlling a drive of a drivenbody by controlling the heating section, the method comprising: a stepof applying an aging treatment to the shape memory alloy which is incontact with the driven body, after the drive apparatus has beenassembled, the aging treatment repeating a predetermined number or moreof times of heating and no-heating processes.
 19. The method ofproducing shape memory alloy of claim 18, wherein the shape memory alloyis heated by applying an electric current to the shape memory alloy. 20.The method of producing shape memory alloy of claim 18, wherein thecontrolling section controls the heating section to heat the shapememory alloy, for applying the aging treatment to the shape memoryalloy.